You cannot voluntarily skip a move in backgammon; you must play every number you legally can. If a roll gives you at least one legal move, you have to make it, even if you would rather not. You only lose a number when there is no legal play for it, for example when both entry points are blocked or a die cannot be used anywhere. If neither die can be played at all, your whole turn is forfeited automatically. This rule matters tactically, because you can sometimes force an opponent into an unwanted move by leaving them only one legal option.